1. Field of the Invention
This invention relates to a picture signal processing method and apparatus, a picture signal recording method and apparatus, and a recording medium, relevant to the expression of a bitstream syntax of the MPEG (Moving Pictures Experts Group) 2 standard which provides seamless reproduction of resolution switching.
2. Description of the Related Art
The MPEG (Moving Pictures Experts Group) 2 is an encoding system used in broadcast or AV equipments, and which has become extremely popular as an information compression technique for pictures/ speech/ data.
In the MPEG 2, input pictures/ speech/ data etc are encoded depending on the bit rate. As for the pictures, each picture is divided in mxc3x97n blocks and transformed by orthogonal transform to concentrate the signal power in order to compress the total information volume.
The picture data, encoded by the MPEG 2, assume a hierarchical structure from a sequence layer to a block layer.
That is, picture data of the MPEG 2 is made up of a sequence layer of a picture group having a series of the same attributes, a GOP (group-of-picture) layer, representing the minimum unit of a picture group as a random-accessing unit, a picture layer of a common attribute to a sole picture, a slice layer of the common information to a small picture obtained on optionally splitting a sole picture, a macro-block layer of the information common to pixel blocks (macro-blocks) obtained on further splitting the slice layer, and a block layer of transform coefficients per se.
Of these, the picture layer has, as its object, a picture of 704(H)xc3x97480(V), in e.g., television signals of the NTSC system, in accordance with the main level format.
The respective pictures are classified into an intra-picture (I-picture), as an intra-coded picture, a forward predictive-coded picture or a P-picture, predictively coded in the forward direction in the display sequence, and a bidirectionally predictivecoded picture or a B-picture, predictive-coded in both the forward and backward directions in the display sequence. These different pictures collectively make up a group-of-pictures (GOP) layer.
Meanwhile, the processing of movies in the MPEG 2, such as resolution switching, is usually carried out in a video sequence unit, which is the minimum unit enabling the definition of resolution.
However, a sequence as a picture source means no other than the video sequence which is a unit defining the resolution. Thus, the encoding size, that is the resolution, cannot be switched by a control operation in the course of the sequence.
The result is that the resolution cannot be switched depending on the sorts of the pictures, such as still pictures or movies undergoing vivid motions, thus worsening the compression efficiency in encoding.
It is therefore an object of the present invention to provide a picture signal processing method and apparatus, a picture signal recording method and apparatus, and a recording medium in which picture signals are switched in resolution depending on the sorts of the pictures, such as still pictures or movies undergoing vivid motions.
The present invention adopts the concept of a movie sequence and prescribes the movie sequence as being a set of video sequences. To this end, the beginning and the end of the movie sequence are clarified. The resolution switching is adapted to be made freely in the movie sequence to improve the compression ratio. Specifically, the same encoding size is used from the beginning to the end of the routine MPEG 2 encoding. According to the present invention, the encoding size is switched appropriately to improve the compression ratio.